How to avoid complaints - Online Help | Zoho Campaigns

How to avoid complaints

In short: spam complaints are the fastest way to wreck your sender reputation, and mailbox providers now enforce a hard limit — keep your complaint rate below 0.3% (aim for under 0.1%). You avoid complaints by mailing only people who opted in, staying relevant and consistent, and making it effortless to unsubscribe so recipients opt out instead of hitting the spam button.
As a growing business, you’re bound to receive complaints from time to time. This guide helps you address the feedback you receive and avoid situations that can be detrimental to your organization.

Avoiding complaints – An infographic.

Complaint life cycle

Complaints are either generated manually or triggered when a recipient marks an email as junk/spam. These complaints are sent to Email Service Providers (ESPs) and Internet Service Providers (ISPs), who then alert the sender. If the recipient complained manually, the ESP/ISP sends the recipient’s details along with the complaint information. Once a recipient marks an email as spam, further emails to that recipient may be classified as spam, quarantined, or rejected, and the ESP adds a negative score to your sender domain. These negative scores hurt your domain’s reputation and can lead to blacklisting. Zoho Campaigns automatically moves the addresses associated with such complaints to the Do-Not-Mail registry, so you don’t email them again.

Complaint types

The following recipient activities count as complaints against your campaigns:
  • Mark as spam: The recipient simply marks the unwanted email as spam. People often choose this when the unsubscribe process feels too complicated — which is why an easy one-click unsubscribe is now both a requirement and your best defense against complaints.
  • Manual complaints: The recipient reports your email to their ISP, a domain’s anti-abuse team, an ESP, or an anti-spam service, usually attaching a copy of the message. People escalate this way when marking as spam hasn’t stopped the unwanted mail.

The complaint-rate threshold

Keep your spam-complaint rate below 0.3% at all times, and treat 0.1% as your real target.

Low or non-existent complaints are ideal. Since February 2024, Google and Yahoo have made the threshold concrete for bulk senders (anyone sending 5,000+ messages a day to their users): your spam-complaint rate must stay under 0.3% — no more than three complaints per 1,000 delivered emails — and providers recommend keeping it below 0.1%. Microsoft applied the same expectation to Outlook.com from May 2025. Cross the line consistently and your mail can be filtered to spam, throttled, or blocked, and your account may be suspended by the ESP or, in severe cases, the ISP. You can monitor your rate in Google Postmaster Tools and Yahoo’s Complaint Feedback Loop.


Tackling complaints

Here are the common reasons for complaints and how to avoid them.
  1. Sending to unopted / uninterested people: Emailing people who never went through a double opt-in leads to complaints. Contact only recipients who actually asked for your newsletters or marketing emails, and never email random or purchased contacts.
  2. Don’t buy mailing lists: Purchasing contacts from third parties does far more harm than good and will spoil your domain’s reputation. Purchased lists also commonly contain spam traps, which compound the damage. Don’t ever buy lists.
  3. Recognition failure: Sometimes a genuinely interested contact doesn’t recognize that the email is from a familiar sender, gets unsure of the source, and marks it as spam. Highlight your brand, keep a consistent from-name, and authenticate your domain so your identity is clear — see Authenticate your sender domain.
  4. Flooding or forgetting your contact’s inbox: Cadence matters. Flooding inboxes invites complaints, but leaving a long gap means contacts forget you and report the next email as spam. Maintain a steady, predictable sending pace.
  5. Irrelevant emails: If someone subscribes to one newsletter but receives every campaign you send, the irrelevant ones will irritate them. Use segments or separate lists and send only what each contact asked for. A preference center that lets people choose topics and frequency reduces both complaints and unsubscribes.
  6. Honor unsubscribes: When a contact opts out, honor it and don’t email them again unless they reach out first. Ignoring opt-outs provokes complaints and blacklisting. Under the current rules you must process unsubscribe requests within two days.
  7. Keep the unsubscribe process simple: Give contacts a comfortable exit. Making unsubscribing hard doesn’t reduce opt-outs — it raises your complaint rate, because people reach for the spam button instead. Bulk senders are now required to offer a one-click unsubscribe (the List-Unsubscribe header defined in RFC 8058); include a visible unsubscribe link in every template.